Plasma amyloid beta protein 1-42 levels are increased in old Down Syndrome but not in young Down Syndrome.

Plasma amyloid beta protein 1-40 (Abeta40) and Abeta42 levels were quantitated from 28 young Down syndrome (DS) (20-40 years old), 28 age-matched controls, 32 old DS (41-65 years old) and 32 age-matched controls in a sandwich enzyme-linked immunosorbent assay. Abeta40 levels were higher in young DS and old DS than controls. Abeta42 levels in young DS and controls were similar, however Abeta42 levels were higher in old DS than controls or young DS. The higher Abeta42 levels in old DS suggests that Abeta42 is selectively increased in plasma concurrently with the development of Alzheimer disease neuropathology.